The present invention relates to an acoustic charge transport (ACT) device; and more particularly, to a digital input structure for an ACT.
The simple structure of an ACT device together with its high charge transport efficiency and self clocking of charges through the device make an ACT device ideally suited for many filtering applications. Because of the popularity of digital signalling processing, in many applications ACT filters must interface with digital signal processing circuits. In such applications, analog-to-digital converters, and digital-to-analog converters are generally required. As with all electronic systems, it is usually desirable to reduce the number of components needed to implement a given signal processing application. There is therefore a need in the industry for an ACT device that directly accepts digital inputs, without the need for a separate digital-to-analog converter.
Recently proposed digital high definition television (HDTV) systems provide an example of systems that can use ACT devices that are capable of directly accepting digital data. It is estimated that such digital HDTV systems will require some 14.4 billion operations per second. To reduce this processing burden, I have proposed, in my co-pending U.S. patent application Ser. No. 07/425,892 entitled "A HIGH DEFINITION TELEVISION/ACOUSTIC CHARGE TRANSPORT FILTER BANK" and that is assigned to the same assignee as this application, using ACT devices to eliminate approximately two-thirds of this processing. But, digital-to-analog converters are needed to interface the ACT devices with the digital signal processing circuitry. Thus, it is desirable to have ACT devices that can be used in HDTV systems such as the recently proposed digital HDTV systems, and that can directly accept digital input data without additional peripheral interface circuits.